The invention relates to the filler neck of a fuel tank with an arrangement for preventing incorrect fueling, composed of a neck body, at least one part which can be moved counter to a spring force by inserting the filler pipe of the correct diameter, a rotatable ring and closing elements which are actuated by said ring, with a transmission device being arranged between the movable part and the rotatable ring.
In motor vehicles with a diesel engine, the risk of incorrect fueling is high because the diameter of the filler pipe of a fueling nozzle for unleaded gasoline is smaller than that of a fueling nozzle for diesel fuel. The correct diameter is therefore the larger diameter, and the following invention concerns very reliably preventing the insertion of a smaller filler pipe into a larger hole.
It is known from EP 1 284 212 B1 for a tube piece which is movable in the longitudinal direction and which has a constriction at the tank side to be provided in the filler pipe, the diameter of which constriction is smaller than that of a filler pipe for diesel fuel but is larger than that of a filler pipe for gasoline. Said tube piece acts via a slotted guide on the closing elements, either directly on movable closing elements or via a rotatable tube piece which surrounds said tube piece.
Said safety device fails, however, if the filler pipe is inserted obliquely, or can be circumvented by pressing laterally on the filler pipe. On account of the guide length required for the two tube pieces, the spatial requirement of a filler neck of said type in the longitudinal direction is considerable and the attachment of further fittings, such as for example valves and branches for escaping fuel vapors, is difficult if not impossible.